Lorentzian1D v1¶

Lorentzian1D dialog.

Table of Contents

Summary
Properties
Description
Source

Summary ¶

== Deprecation notice == Instead of using this algorithm to fit a Lorentzian please use the Fit algorithm where the Function parameter of this algorithm is used to specified the fitting function, including selecting a Lorentzian.

Properties ¶

Name	Direction	Type	Default	Description
InputWorkspace	Input	MatrixWorkspace	Mandatory	Name of the input Workspace
WorkspaceIndex	Input	number	0	The Workspace to fit, uses the workspace numbering of the spectra (default 0)
StartX	Input	number	Optional	A value of x in, or on the low x boundary of, the first bin to include in the fit (default lowest value of x)
EndX	Input	number	Optional	A value in, or on the high x boundary of, the last bin the fitting range (default the highest value of x)
BG0	InOut	number	0	Constant background value (default 0)
BG1	InOut	number	0	Linear background modelling parameter (default 0)
Height	InOut	number	0	height of peak (not the height may be refined to a negative value to fit a dipped curve)
PeakCentre	InOut	number	0	Centre of peak (default 0)
HWHM	InOut	number	1	half-width at half-maximum (default 1)
Fix	Input	string		A list of comma separated parameter names which should be fixed in the fit
MaxIterations	Input	number	500	Stop after this number of iterations if a good fit is not found
OutputStatus	Output	string
OutputChi2overDoF	Output	number
Output	Input	string		If not empty OutputParameters TableWorksace and OutputWorkspace will be created.

Description ¶

Takes a histogram in a 2D workspace and fit it to a Lorentzian function, i.e. to the function:

$\mbox{BG0}+\mbox{BG1}*x+\mbox{Height}* \left( \frac{\mbox{HWHM}^2}{(x-\mbox{PeakCentre})^2+\mbox{HWHM}^2} \right)$

where

BG0 - constant background value
BG1 - constant background value
Height - height of peak (at maximum)
PeakCentre - centre of peak
HWHM - half-width at half-maximum

Note that the FWHM (Full Width Half Maximum) equals two times HWHM, and the integral over the Lorentzian equals $\mbox{Height} * \pi * \mbox{HWHM}$ (ignoring the linear background). In the literature you may also often see the notation $\gamma$ = HWHM.